Synthesis of chloropentafluoroethane

ABSTRACT

The invention relates to a gas phase process for the manufacture of chloropentafluoroethane by the action of hydrofluoric acid on dichlorotetrafluoroethane in the presence of a catalyst, the said catalyst being prepared by reacting, in a gaseous phase, an alumina in which the sodium oxide content is below 300 ppm and the volume of the pores having a radius equal to 40 angstroms or above is greater than 0.7 cm 3  /g, with hydrofluoric acid or with a mixture of hydrofluoric acid and of air, nitrogen or a fluorinated compound.

TECHNICAL FIELD

The present invention relates to the manufacture of chloropentafluoroethane (C₂ F₅ Cl) by a gas phase catalysed reaction of dichlorotetrafluoroethane (C₂ F₄ Cl₂) with hydrofluoric acid (HF).

BACKGROUND ART

Chloropentafluoroethane, which is used as a solvent, propellant or refrigerant fluid, is prepared by known processes, for example from perchloroethylene, chlorine and hydrofluoric acid (East German Pat. No. 117,580) or by a gas phase reaction of trichlorotrifluoroethane C₂ F₃ Cl₃ with hydrofluoric acid in the presence of aluminium trifluoride (Japanese Publication No. 48-26,729/73).

U.S. Pat. No. 3,087,974 describes the vapor phase disproportionation of chlorofluoro compounds on a catalyst without the addition of hydrofluoric acid. The disproportionation of dichlorotetrafluoroethane takes place according to the reaction:

    2C.sub.2 Cl.sub.2 F.sub.4 →C.sub.2 ClF.sub.5 +C.sub.2 Cl.sub.3 F.sub.3

This catalyst is activated alumina of high surface area which is treated with a fluorocarbon compound before being used for the disproportionation reaction. The conversion of CF₂ ClCF₂ Cl to C₂ ClF₅ does not exceed 34% on a molar basis and a high proportion of C₂ Cl₃ F₃ is produced as a by-product.

U.S. Pat. No. 3,258,500 describes a vapour phase catalysed fluorination using hydrofluoric acid. The dichlorotetrafluoroethane (CF₂ Cl--CF₂ Cl) and hydrofluoric acid (HF), in a molar ratio [HF/CF₂ Cl--CF₂ Cl] of between 4 and 5, react at 400° C. on a chromium oxide catalyst. The proportion of hexafluoroethane C₂ F₆ formed is 0.19 on a molar basis relative to C₂ F₅ Cl.

A paper by L. Marangoni et al., "Preparation of chloropentafluoroethane from dichlorotetrafluoroethane" (Journal of Fluorine Chemistry 19, 1981/82, pages 21 to 34) also describes a chromium oxide-based catalyst for the gas phase manufacture of C₂ F₅ Cl from C₂ F₄ Cl₂ and HF. The degree of conversion of C₂ Cl₂ F₄ is between 72 and 75%, the yield of C₂ F₅ Cl is between 89 and 92%, but the formation of hexafluoroethane is still 8% on a molar basis of the formation of C₂ F₅ Cl.

A paper by M. Vecchio et al., "Studies on a vapor-phase process for the manufacture of chlorofluoro-ethanes" (Journal of Fluorine Chemistry, 4, 1974, pages 111 to 139) describes the same reaction as the preceding paper but on a catalyst based on aluminium fluoride doped with nickel, iron and chromium halides. The degree of conversion of C₂ F₄ Cl₂ does not exceed 41% and the molar pourcentage of C₂ F₅ Cl at the reactor outlet is 38%.

The catalysts of the prior art are difficult to prepare, while the yields and selectivities for C₂ F₅ Cl are mediocre.

The present invention overcomes all these disadvantages by offering a simple, flexible and economical process for producing C₂ F₅ Cl.

SUMMARY OF THE INVENTION

The invention relates to a process for synthesizing chloropentafluoro ethane which comprises reacting dichlorotetrafluoro ethane with hydrofluoric acid over a fluorinated alumina catalyst prepared from an activated alumina having a sodium oxide content below 300 ppm and a volume of the pores with a radius of 40 angstroms or above greater than 0.7 cm³ /g.

In this process, the reaction is carried out at a temperature range of between 350° and 550° C. at a molar ratio of hydrofluoric acid to dichlorotetrafluoro ethane of between about 0.5 and 1.5, with a reaction pressure between about 0.5 and 4 bars absolute and a reaction time of between about 5 and 15 seconds.

The fluorinated alumina catalyst is prepared by reacting the activated alumina with hydrofluoric acid or with a mixture of hydrofluoric acid and of air, nitrogen or a fluorinated compound at a sufficient temperature and pressure and for a sufficient reaction time to convert at least 70 percent by weight (preferably 90% or more) of the alumina to aluminium trifluoride.

DETAILED DESCRIPTION OF THE INVENTION

The process according to the invention includes subjecting C₂ Cl₂ F₄ to the action of HF in gaseous phase in the presence of a catalyst prepared by reacting an activated alumina in which the sodium oxide content is below 300 ppm and the volume of the pores with a radius of 40 angstroms and more is greater than 0.7 cm³ /g with hydrofluoric acid or with a mixture of hydrofluoric acid and of air, nitrogen or a fluorinated compound such as, for example, dichlorotetrafluoroethane.

A high conversion, above 80%, of the starting materials and a high yield of C₂ F₅ Cl are obtained. Another advantage of the process is increased catalyst life.

The activated aluminas are produced by controlled heating of alumina hydrates so as to remove most of the water of formation (Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd edition, vol. 2, page 225).

The alumina used to prepare the catalyst is a commercially available alumina. It suffices to choose an activated alumina in which the sodium oxide content is below 300 ppm and the volume of pores with a radius equal to or greater than 40 Å is above about 0.7 cm³ /g and preferably between 0.75 and 1 cm³ /g. It is advantageous for the alumina to be in the form of granules, beads or extrudates of a size smaller than 20 mm diameter spheres and preferably a few (i.e., 0.5-3) millimeters, to permit convenient handling during the loading and draining of the reactor.

As previously stated, the Na₂ O content of the alumina must be less than about 300 ppm and preferably, as low as practically possible. It is also advantageous to choose an alumina which contains, on a weight basis, not more than 0.5% of silica and 0.2% of iron oxide (Fe₂ O₃). This alumina is converted into a mixture of at least 70%, preferably 90% or more of aluminium trifluoride (AlF₃), remainder unconverted alumina, by reaction with HF by itself or mixed with air, nitrogen or a fluorinated compound.

For example, it is possible to use a mixture of C₂ Cl₂ F₄ and hydrofluoric acid, which is passed over this alumina at a sufficient temperature to initiate a reaction which converts the alumina to aluminium trifluoride. It is advantageous to operate between 150° and 500° C. The operation is preferably performed at atmospheric pressure, with contact times of between 5 and 15 seconds. The specialist can easily carry out the reaction and adjust the proportions of C₂ F₄ Cl₂ and HF, the temperature, the pressure and the contact time so as to prevent the alumina being damaged by a high temperature due to the exotherm of the reaction.

When the composition of the gases no longer changes after passing over this alumina, then this indicates that the alumina has been converted to the catalyst. It can be washed with water if appropriate, before being used to effect the fluorination of C₂ F₄ Cl₂ to C₂ F₅ Cl according to the invention.

According to a preferred embodiment of the invention the catalyst may also be prepared by subjecting alumina in a fluidized bed to the action of a stream of hot air containing hydrofluoric acid. It is advantageous to operate between 150° and 500° C. A mixture of between 0.1 and 30%, on a molar basis, of HF with air, and preferably between 1.5 and 3%, is advantageously employed. The throughput is advantageously between 200 and 250 moles/hour per liter of catalyst. The operation is preferably carried out at atmospheric pressure at temperature of 350° C. or above. It is convenient to vary the HF concentration in the air to control the exotherm of the reaction. When no more HF is consumed, the reaction is stopped and the catalyst is considered to be ready for the fluorination of C₂ F₄ Cl₂.

The reaction between C₂ F₄ Cl₂ and anhydrous HF is carried out in gaseous phase over the catalyst which may be prepared according to either of the above two routes. The reaction temperature is advantageously between 350° and 550° C. and preferably between 380° and 500° C. The molar ratio HF/C₂ Cl₂ F₄ is advantageously between 0.5 and 1.5 and preferably between 0.9 and 1.1. While the operation may be carried out at any pressure, provided that it remains in gaseous phase, it is nevertheless much simpler to operate between 0.5 and 4 bars absolute, and preferably at atmospheric pressure or thereabouts, and with a contact time of between 5 and 15 seconds and preferably between 6 and 13 seconds.

EXAMPLES

The following examples illustrate the invention without limiting it.

In all these examples, the C₂ F₄ Cl₂ employed contains 92.7% of the symmetrical isomer.

Example 1

A pure activated alumina supplied by the Kaiser Company (ref. Al 4192) in the form of 0.8 mm (1/32") extrudates is employed, the characteristics of which are as follows:

    ______________________________________                                         Volume of pores with a radius greater                                                                   0.91 cm.sup.3 /g                                      than or equal to 40Å =                                                     Total BET specific surface =                                                                            161 m.sup.2 /g                                        Mean pore radius =       106Å                                              Apparent density (compacted bulk) =                                                                     0.47                                                  Surface area of pores with a radius                                                                     105 m.sup.2 /g                                        between 50 and 250Å =                                                      Fe.sub.2 O.sub.3 content:                                                                  0.08% by weight                                                    SiO.sub.2 content:                                                                         0.13% by weight                                                    Na.sub.2 O content:                                                                        0.015% by weight.                                                  ______________________________________                                    

0.12 liter of this alumina is charged as a fixed bed into a tubular reactor with an internal diameter of 28 mm, and it is then converted into catalyst by proceeding as in the table below.

    ______________________________________                                         Temper-          Molar through-                                                ature  Absolute  put of reactants     Time                                     in the pressure  in moles/(hr × 100                                                                     Contact                                                                               (hrs)                                    reactor                                                                               (atmos-   ml of catalyst)                                                                              time   cumu-                                    (°C.)                                                                          pheres)   C.sub.2 Cl.sub.2 F.sub.4                                                                 HF    (seconds)                                                                             lative                                 ______________________________________                                         350    1         0.374     0.177 12.8   48                                     380    1         0.328     0.178 12.7   93                                     410    1         0.337     0.187 12.2   142                                    ______________________________________                                    

At the end of this treatment, after the oxygenfree acids have been scrubbed with water and with an aqueous sodium hydroxide solution, the proportion of C₂ ClF₅ in the gas leaving the reactor reaches 23.6%, whereas it was only 0.7% at 350° C.

The reactor temperature is then raised to 450° C., the C₂ Cl₂ F₄ being of the same quality as before. The results are given in Table I below, where the molar through-puts are expressed per 0.1 liter of catalyst, the reactor pressure being 1 bar absolute, and the temperature being maintained at 450° C. The working time of the catalyst which is shown includes the preliminary step of conversion of alumina into catalyst.

In all the tests described above, the unconverted dichlorotetrafluoroethane (approximately 15% on a molar basis of the C₂ Cl₂ F₄ compound employed) contains 20 to 25% of the symmetrical isomer CF₂ Cl--CF₂ Cl.

After 550 hours operation under the working conditions described above, and a regeneration with pure air at 450° C., the catalyst produces results which are absolutely identical to the above.

Example 2

The same activated alumina as in Example 1, in the same physical form of 0.8 mm extrudates, is taken and is converted into catalyst by a fluidized bed technique. 0.125 liter of Kaiser 4192 alumina (51.3 g) is taken and heated to 350° C. in a stream of nitrogen, and the following gas mixture is then introduced for 24 hours at atmospheric pressure:

air: 27.2 moles/h

HF: 0.77 moles/h.

After 24 hours of this treatment, the catalyst contains 62% of fluorine, that is to say 91.4% of aluminium fluoride and 8.6% of unconverted alumina. Its weight is 77.9 grams.

68.1 grams of this catalyst (0.1 liter) are taken to be tested in the same 28 mm diameter tubular reactor as in Example 1, and the procedure of Example 1 is followed. The results are shown in Table II below.

The catalyst working time which is shown in this table corresponds to the period beginning with the charging of the reactor with a fixed bed and does not include the conversion of alumina into catalyst.

Example 3

The method of Example 2 is followed, starting with the same activated alumina, except that after the conversion of the alumina into catalyst and charging the reactor with a fixed bed for the fluorination of C₂ F₄ Cl₂, the reaction is started with a molar ratio HF/C₂ Cl₂ F₄ close to 1 instead of 0.4 in Example 2.

The results are shown in Table III.

The starting method does not alter the catalyst's activity or selectivity.

The working time shown is the period from the charging of the reactor with a fixed bed and does not include the conversion of alumina into catalyst.

Example 4 (comparative)

The procedure of Example 2 is followed but using an activated alumina whose pore volume is different from that of the activated alumina used in the process according to the invention; the alumina used is SCM 250, the characteristics of which are:

Chemical purity:

Na₂ O: 800 ppm

Fe₂ O₃ : 300 ppm

SiO₂ : 200 ppm

Physical properties:

Form: beads, 2 to 4 mm in diameter

Specific surface (BET)=270 m² /g

Total volume of pores of radius greater than or equal to 40 Å=0.63 cm³ /g

Mean pore diameter 90 Å

Bulk density: 0.66 g/ml.

A catalyst is obtained whose AlF₃ content is 87.7% by weight, the remainder being unconverted alumina. The results are shown in Table IV,1; the working times are measured as in Example 2.

The same SCM 250 alumina is used as spheres of 2 to 4 mm and is converted into catalyst as before, but after the conversion it is reduced mechanically into small pieces of less than 1 mm to approach the size of the Kaiser alumina of Examples 1, 2 and 3. This catalyst is then used as before.

The results are shown in Table IV,2.

The working times shown in the table do not include the time for converting the alumina to catalyst.

Example 5

CS 331-1 alumina sold by the Catalysts and Chemicals Europe (CCE) company is employed.

Its chief physical characteristics are as follows:

form: extrudates 1/16" (1.6 mm) in diameter

active surface area (BET): 255 m² /g

mean pore diameter: 90 Å

volume of pores of radius greater than or equal to 40 Å: 0.76 cm³ /g

bulk density: 0.60 g/ml.

Na₂ O: 200 ppm

Fe₂ O₃ : 800 ppm

SiO₂ : 300 ppm

The catalyst is prepared as in Example 2, the AlF₃ concentration of the catalyst is 92%, with 8% unconverted alumina.

The results of the corresponding tests are shown in Table No. V below; the results obtained are found to be clearly superior to those obtained in comparative Example No. 4 (SCM 250 alumina).

                                      TABLE I                                      __________________________________________________________________________                             RESULTS OBTAINED                                                                                                Specific              OPERATING CONDITIONS                                     output                Catalyst                        Degree of                                                                            Molar Molar                                                                               Molar   in grams              working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio ratio                                                                               ratio   of C.sub.2                                                                     ClF.sub.5             time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 /                                                                    C.sub.2 F.sub.3 Cl.sub.3                                                            CF.sub.4 + CF.sub.3                                                                    per hour              (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 ClF.sub.5                                                                 C.sub.2 ClF.sub.5                                                                    C.sub.2 ClF.sub.5                                                                   C.sub.2 ClF.sub.5                                                                      per liter             hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                        (× 100)                                                                       (× 100)                                                                          of                    __________________________________________________________________________                                                              catalyst              165   0.132                                                                             0.330                                                                               0.40 13.1 90.0                                                                              76.9 62.0  0.5   20.1 0.2     316                   257   0.268                                                                             0.257                                                                               1.04 11.6 79.3                                                                              85.2 81.4  0.6   3.9  0.1     310                   445   0.254                                                                             0.283                                                                               0.90 11.3 73.1                                                                              85.5 81.7  0.5   4.0  0.1     351                   __________________________________________________________________________

                                      TABLE II                                     __________________________________________________________________________                        RESULTS OBTAINED                                                                                         Specific                          OPERATING CONDITIONS                         output                            Catalyst                   Degree of                                                                            Molar  Molar                                                                               in grams                          working                                                                              Molar through-       conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5              time  put of reactants                                                                       Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3 /                                                          per hour                          (cumulative                                                                          (moles/hour)                                                                           time conversion %                                                                           to C.sub.2 ClF.sub.5                                                                 C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                         hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                       __________________________________________________________________________     23.5  0.140                                                                             0.377                                                                               11.8 89.3                                                                              80.4 64.7  1.1    19.2 377                               46.5  0.149                                                                             0.365                                                                               11.8 91.1                                                                              80.5 65.1  1.2    18.8 367                               66.5  0.140                                                                             0.360                                                                               12.2 93.4                                                                              79.6 63.8  0.7    20.0 354                               89.5  0.244                                                                             0.247                                                                               12.4 79.5                                                                              87.9 80.8  1.0    5.5  309                               111.5 0.223                                                                             0.247                                                                               12.9 80.2                                                                              87.2 79.6  1.0    6.0  304                               133.5 0.218                                                                             0.247                                                                               13.0 83.1                                                                              85.8 77.2  1.0    7.5  295                               __________________________________________________________________________      Operating conditions                                                           Fixed bed catalyst (volume = 0.1 liter)                                        Temperature: 450° C.                                                    Pressure: atmospheric                                                    

                                      TABLE III                                    __________________________________________________________________________                             RESULTS OBTAINED                                                                                         Specific                     OPERATING CONDITIONS                              output                       Catalyst                        Degree of                                                                            Molar  Molar                                                                               in grams                     working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5         time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3                                                            per hour                     (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 ClF.sub.5                                                                 C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                    hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                  __________________________________________________________________________     24    0.255                                                                             0.243                                                                               1.05 13.2 75.4                                                                              86.5 79.8  1.2    4.5  300                          47    0.240                                                                             0.245                                                                               0.98 12.5 76.8                                                                              86.7 79.9  0.9    5.2  302                          __________________________________________________________________________      Operating conditions                                                           Fixed bed catalyst (volume = 0.1 liter) prepared as in Example No. 2           Temperature = 450° C.                                                   Pressure: atmospheric                                                    

                                      TABLE IV,1                                   __________________________________________________________________________                             RESULTS OBTAINED                                                                                         Specific                     OPERATING CONDITIONS                              output                       Catalyst                        Degree of                                                                            Molar  Molar                                                                               in grams                     working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5         time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3                                                            per hour                     (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 ClF.sub.5                                                                 C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                    hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                  __________________________________________________________________________     24    0.240                                                                             0.243                                                                               0.99 12.5 9.0                                                                               9.4  6.8   5.8    4.3  25                           48    0.235                                                                             0.253                                                                               0.93 12.4 10.0                                                                              10.3 8.2   2.4    3.6  32                           71    0.249                                                                             0.253                                                                               0.98 12.1 12.7                                                                              10.3 7.9   1.9    3.7  31                           __________________________________________________________________________       Operating conditions common to the tests                                      Fixed bed catalyst (volume = 0.1 liter) in the form of 2 to 4 mm beads         Temperature = 450° C.                                                   Atmospheric pressure                                                     

                                      TABLE IV,2                                   __________________________________________________________________________                             RESULTS OBTAINED                                                                                         Specific                     OPERATING CONDITIONS                              output                       Catalyst                        Degree of                                                                            Molar  Molar                                                                               in grams                     working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5         time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3                                                            per hour                     (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 Cl.sub.2 F.sub.5                                                          C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                    hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                  __________________________________________________________________________     117   0.232                                                                             0.233                                                                               1.0  13.0 9.5                                                                               10.6 8.4   0.6    2.3  30                           139   0.239                                                                             0.234                                                                               1.0  12.8 8.9                                                                               10.3 8.0   0.6    2.4  29                           Temperature = 500° C. after                                             the 139th hour                                                                 159   0.238                                                                             0.230                                                                               1.0  12.1 10.9                                                                              20.3 17.2  1.5    1.1  61                           __________________________________________________________________________      Operating conditions                                                           Fixed bed catalyst (volume = 0.1 liter)                                        Temperature = 450° C. up to the 139th hour, then 500° C.         Atmospheric pressure                                                     

                                      TABLE V                                      __________________________________________________________________________                             RESULTS OBTAINED                                                                                         Specific                     OPERATING CONDITIONS                              output                       Catalyst                        Degree of                                                                            Molar  Molar                                                                               in grams                     working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5         time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3                                                            per hour                     (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 Cl.sub.2 F.sub.5                                                          C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                    hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                  __________________________________________________________________________     25    0.245                                                                             0.242                                                                               1.0  12.5 67.7                                                                              76.9 71.5  1.7    5.3  268                          48    0.245                                                                             0.245                                                                               1.0  12.4 66.4                                                                              77.0 71.0  1.0    5.4  268                          71    0.245                                                                             0.245                                                                               1.0  12.4 66.8                                                                              76.9 70.7  1.0    5.7  268                          86.5  0.194                                                                             0.243                                                                               0.8  13.9 66.2                                                                              78.3 70.8  1.2    7.5  266                          __________________________________________________________________________      Operating conditions                                                           Fixed bed catalyst (volume = 0.1 liter) in the form of 1.6 mm extrudates,      prepared as in Example No. 2                                                   Temperature = 450° C.                                                   Atmospheric pressure                                                     

                                      TABLE VI                                     __________________________________________________________________________                             RESULTS OBTAINED                                                                                         Specific                     OPERATING CONDITIONS                              output                       Catalyst                        Degree of                                                                            Molar  Molar                                                                               in grams                     working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5         time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3                                                            per hour                     (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 Cl.sub.2 F.sub.5                                                          C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                    hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                  __________________________________________________________________________     24    0.357                                                                             0.358                                                                               1.0  11.8 7.0                                                                               0.2  0.1   0      0    0.4                          47    0.351                                                                             0.378                                                                               0.9  11.6 2.0                                                                               0.1  0.1   0      0    0.4                          70    0.351                                                                             0.376                                                                               0.9  11.6 4.1                                                                               0.1  0.1   0      0    0.4                          92    0.360                                                                             0.368                                                                               1.0  10.8 5.4                                                                               0.2  0.1   0      0    0.4                          __________________________________________________________________________      Operating conditions                                                           Catalysts in the form of a fluid bed (volume = 0.14 liter) with a mean         particle size of 50 to 80 microns                                              Temperature = 450° C.                                                   Atmospheric pressure                                                     

                                      TABLE VII                                    __________________________________________________________________________                             RESULTS OBTAINED                                                                                         Specific                     OPERATING CONDITIONS                              output                       Catalyst                        Degree of                                                                            Molar  Molar                                                                               in grams                     working                                                                              Molar through-                                                                         Molar             conversion                                                                           ratio  ratio                                                                               of C.sub.2 ClF.sub.5         time  put of reactants                                                                       ratio                                                                               Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 F.sub.6 + CF.sub.4 /                                                          C.sub.2 F.sub.3 Cl.sub.3                                                            per hour                     (cumulative                                                                          (moles/hour)                                                                           HF/  time conversion %                                                                           to C.sub.2 Cl.sub.2 F.sub.5                                                          C.sub.2 ClF.sub.5                                                                     C.sub.2 ClF.sub.5                                                                   per liter                    hours)                                                                               HF C.sub.2 Cl.sub.2 F.sub.4                                                            C.sub.2 Cl.sub.2 F.sub.4                                                            (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            %     (× 100)                                                                         (× 100)                                                                       of catalyst                  __________________________________________________________________________     24    0.349                                                                             0.375                                                                               0.93 8.4  60.3                                                                              65.4 60.2  1.0    7.5  348.8                        48    0.367                                                                             0.373                                                                               0.98 8.2  59.5                                                                              67.2 62.5  0.5    7.0  360.2                        72.45 0.521                                                                             0.501                                                                               1.04 5.9  51.7                                                                              60.9 57.1  0.5    6.1  442.0                        95.45 0.500                                                                             0.495                                                                               1.01 6.4  54.4                                                                              62.7 58.5  0.7    6.7  447.4                        __________________________________________________________________________      Operating conditions                                                           Fixed bed catalysts (volume = 0.1 liter) in the form of 0.8 mm extrudates      Temperature = 450° C.                                                   Atmospheric pressure                                                     

                                      TABLE VIII                                   __________________________________________________________________________                              RESULTS OBTAINED                                      OPERATING CONDITIONS             Degree of                                                                            Molar                                                                               Specific output                        Molar throughput             conversion                                                                           ratio                                                                               in grams of                                                                    C.sub.2 ClF.sub.5                  Na.sub.2 O                                                                         of reactants                                                                            Molar  Contact                                                                             Degree of                                                                              of C.sub.2 Cl.sub.2 F.sub.4                                                          C.sub.2 Cl.sub.3 F.sub.3 /                                                          per hour per                       content                                                                            (moles/hour)                                                                            ratio  time conversion %                                                                           to C.sub.2 ClF.sub.5                                                                 C.sub.2 ClF.sub.5                                                                   liter of                           (ppm)                                                                              HF  C.sub.2 Cl.sub.2 F.sub.4                                                            HF/C.sub.2 Cl.sub.2 F.sub.4                                                           (seconds)                                                                           HF C.sub.2 Cl.sub.2 F.sub.4                                                            (%)   (× 100)                                                                       catalyst                           __________________________________________________________________________     150 0.449                                                                              0.429                                                                               1.05   7.4  52.1                                                                              61.1 57.9  5.5  383.8                              930 0.411                                                                              0.428                                                                               0.96   7.2   7.8                                                                               8.1  7.7  5.2   50.9                              __________________________________________________________________________      Operating conditions                                                           Fixed bed catalysts (volume = 0.1 liter) in the form of 0.8 mm extrudates      Temperature = 450° C.                                                   Atmospheric pressure                                                     

The working times shown do not include the conversion of alumina into catalyst.

Example 6 (comparative)

Fluorination of C₂ F₄ Cl₂ with HF according to a process not in accordance with the invention.

Instead of taking an alumina and converting it into catalyst as previously, a commercial aluminium trifluoride powder containing approximately 8% of alumina is used.

Its chief physicochemical characteristics are as follows:

mean particle size of the powder: 50 to 80 microns

total specific area (BET)=1.6 m² /g

volume of pores of radius greater than or equal to 40 Å: 0.25 cm³ /g.

After this, the procedure is as in the preceding examples of the fluorination of C₂ F₄ Cl₂ with HF, but in a fluid bed instead of a fixed bed.

The results appear in Table VI.

Example 7

The procedure of Example 2 is followed, using the same type of alumina (Kaiser 4192), but working with a shorter contact time.

The results are shown in Table VII, where the working times do not include the time for converting the alumina into catalyst.

It is found that the specific output of C₂ ClF₅ can be considerably increased without harming the yield.

Table VIII collates results obtained under analogous operating conditions and shows the effect of the Na₂ O content.

While it is apparent that the invention herein disclosed is well calculated to fulfill the desired results, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art, and it is intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention. 

What is claimed is:
 1. A process for the manufacture of chloropentafluoroethane which comprises subjecting dichlorotetrafluoroethane to the action of hydrofluoric acid in gaseous phase in the presence of a fluorinated alumina catalyst, said catalyst being prepared by reacting in gaseous phase an activated alumina in which the sodium oxide content is below 300 ppm and the volume of the pores having a radius of 40 angstroms or above is greater than 0.7 cm³ /g, with hydrofluoric acid or with a mixture of hydrofluoric acid and of air, nitrogen or a fluorinated compound.
 2. The process of claim 1 wherein the fluorinated alumina catalyst is prepared from an alumina in which the volume of the pores having a radius of 40 angstroms or above is between 0.75 and 1 cm³ /g.
 3. The process of claim 1 wherein the fluorinated alumina catalyst is prepared from an alumina containing less than 0.5 weight percent silica and less than 0.2 weight percent iron oxide.
 4. The process of claim 1 wherein the fluorinated alumina catalyst is prepared from an alumina in the form of particles having sizes smaller than 20 mm diameter spheres.
 5. The process of claim 1 wherein the fluorinated alumina catalyst is prepared by reacting the alumina with a mixture of air and hydrofluoric acid at a temperature of between 150° and 500° C.
 6. The process of claim 5 wherein the molar proportion of hydrofluoric acid in the mixture air-HF is between about 0.1 and 30 percent.
 7. The process of claim 5 wherein the molar proportion of hydrofluoric acid in the mixture air-HF is between about 1.5 and 3 percent.
 8. The process of claim 5 wherein the reaction is effected at atmospheric pressure and at a temperature of 350° C. or above.
 9. The process of claim 1 wherein the fluorinated alumina catalyst is prepared by passing over the alumina a gaseous mixture of hydrofluoric acid and dichlorotetrafluoroethane at a temperature of between 150° and 500° C.
 10. The process of claim 9 wherein the operation is effected at atmospheric pressure with a contact time of between about 5 and 15 seconds.
 11. A process for the manufacture of chloropentafluoroethane which comprises:preparing a fluorinated alumina catalyst by reacting an activated alumina having a sodium oxide content below 300 ppm and a volume of the pores with a radius of 40 angstroms or above greater than 0.7 cm³ /g, with a mixture of air and hydrofluoric acid at a temperature of between about 150° and 500° C. and atmospheric pressure, until no more HF is consumed; and passing over this catalyst hydrofluoric acid and dichlorotetrafluoroethane at a temperature of between about 350° and 550° C. and a pressure of between about 0.5. and 4 bars absolute for a contact time of between about 5 and 15 seconds.
 12. The process of claim 11 wherein the molar ratio of hydrofluoric acid to dichlorotetrafluoroethane is between about 0.5 and 1.5.
 13. The process of claim 11 wherein the reaction pressure is atmospheric.
 14. A process for the manufacture of chloropentafluoroethane which comprises:preparing a fluorinated alumina catalyst by reacting an activated alumina having a sodium oxide content below 300 ppm and a volume of the pores with a radius of 40 angstroms or above greater than 0.7 cm³ /g, with a gaseous mixture of hydrofluoric acid and dichlorotetrafluoro ethane at a temperature of between about 150° and 500° C. and atmospheric pressure, until the composition of the outgoing gases no longer changes; and passing over this catalyst hydrofluoric acid and dichlorotetrafluoroethane at a temperature of between about 350° and 500° C. and a pressure of between about 0.5 and 4 bars absolute for a contact time of between about 5 and 15 seconds.
 15. The process of claim 14 wherein the reaction pressure is atmospheric.
 16. The process of claim 14 wherein the molar ratio of hydrofluoric acid to dichlorotetrafluoroethane is between about 0.5 and 1.5.
 17. A process for the manufacture of chloropentafluoroethane which comprises:preparing a fluorinated alumina catalyst by reacting an activated alumina in the form of particles having a size smaller than 20 mm diameter spheres and having a sodium oxide content below 300 ppm, a silica content of less than 0.5 weight percent, an iron oxide content of less than 0.2 weight percent, and a volume of the pores with a radius of 40 angstroms of above greater than 0.7 cm³ /g, with a gaseous mixture of hydrofluoric acid and a fluorinated compound wherein the weight ratio of hydrofluoric acid to the fluorinated compound is between about 0.5 and 1.5 at a temperature of between about 150° and 500° C. and atmospheric pressure to convert at least 70% by weight of the alumina to aluminum trifluoride, and passing over this catalyst hydrofluoric acid and dichlorotetrafluoroethane at a temperature of between about 350° and 500° C. and a pressure of between about 0.5 and 4 bars absolute for a contact time of between about 5 and 15 seconds to form chloropentafluoroethane at a rate of conversion of at least about 80%. 